Packaging for high purity solvents

ABSTRACT

A container includes an external package and a sealed flexible bag, adapted to hold liquid contents, retained within the external package. The bag is made from a polymer film, which prior to being formed into a bag, was a two dimensional film to which was applied a PECVD SiOx coating.

BACKGROUND OF THE INVENTION

The present disclosure relates to containers and methods of making thesame. More particularly, the present disclosure relates to containerssuitable for packaging high purity solvents, such as hexane, and the useof chemical vapor deposition technology, for example plasma enhancedchemical vapor deposition, for providing a solvent, oxygen, or otherbather for such containers.

High purity solvents have many industrial applications, for example, inanalytical chemistry, environmental analysis and biotechnology. Thesesolvents are typically stored in glass containers (e.g., bottles orother vessels), because the inert property of glass makes it ideal forstoring high purity solvents. However, traditional glass solventcontainers are prone to breakage or degradation during manufacture,filling operations, shipping and use, which means that glassparticulates may enter the solvent, thus degrading the solvent's purity.

While plastic containers are less prone to breakage, their use asprimary packaging for high purity solvents may be limited due to theirgas (e.g., oxygen) permeability. The permeability of plastics to gasesis significantly greater than that of glass and therefore may beunacceptable as primary packaging for high purity solvents. Further,some high purity solvents, such as hexane, for example, tend to degradeand eat through plastic containers.

The problem of permeability and degradation has been addressed in someapplications (for example, pharmaceutical packaging), by adding abarrier coating or layer to a plastic package where it contacts fluidcontents of the package. One such barrier layer is a very thin coatingof SiO_(x), applied, for example, by plasma enhanced chemical vapordeposition (“PECVD”). The advantage of using a SiO_(x) barrier coatingor layer on, e.g., a plastic vessel, is that in several respects,favorable aspects of both glass and plastic are combined into onepackage.

An SiO_(x) barrier coating or layer contains silicon, oxygen, andoptionally other elements. Barrier coatings and processes of applyingthem to substrates, e.g., pharmaceutical packages, are described, e.g.,in U.S. Pat. No. 7,985,188, which is incorporated herein by reference inits entirety.

While a SiO_(x)-coated plastic container is preferable to an uncoatedplastic container for storing high purity solvents, standard containershave drawbacks. For example, three dimensional containers that undergoSiO_(x) coating of their interior surfaces may not be uniformly coated,both in terms of coating thickness and coverage. For example, there ispotential that the SiO_(x) coating may miss spots along the interiorsurfaces of a plastic container. Just as a chain is only as strong asits weakest link, a purportedly SiO_(x)-coated plastic container inwhich even tiny portions of the interior surface are uncoated or haveother imperfections, may be subject to degradation at those vulnerablespots by the contents of the container, e.g., a high purity solvent suchas hexane. Accordingly, there is a need for a three dimensionalcontainer, e.g., for containing high purity solvents, that is betteradapted for more uniform and complete SiO_(x) coating, e.g., usingPECVD, than standard three dimensional plastic containers.

SUMMARY OF THE INVENTION

Accordingly, in one aspect, there is provided a container comprising anexternal package, e.g., a box, comprising therein a sealed flexible bag.The bag comprises a film, e.g., a polyethylene film, which, prior tobeing formed into a three dimensional sealed bag adapted to hold liquidcontents, is a two dimensional film. Preferably, the two dimensionalfilm is substantially free of surface imperfections. A SiO_(x) coatingis applied, e.g. using PECVD, to the two dimensional film before thefilm is formed into a bag. In one aspect, the SiO_(x) coating on the twodimensional film, which is formed into a sealed three dimensional bag,is less prone to imperfections, missed spots and cracking than aconventional three dimensional SiO_(x) coated plastic container. Thus,in one aspect, the invention represents an improvement over conventionalthree dimensional glass or plastic containers for holding high puritysolvents.

Other aspects of the invention will be apparent from this disclosure andthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exploded perspective view of a container accordingto the present invention, with the flexible bag 18 partially cut away toillustrate its interior.

FIG. 2 illustrates an axial sectional view of an apparatus for applyinga PECVD SiO_(x) coating on a two-dimensional flexible polymer film roll,wherein the film, in subsequent processing steps is severable intosections and wherein one or more sections may be combined to form astorage bag that may be used according to the present invention.

FIG. 3 illustrates an axial sectional view of an alternative apparatusfor applying a PECVD SiO_(x) coating on a two-dimensional flexiblepolymer film roll, wherein the film, in subsequent processing steps isseverable into sections and wherein one or more sections may be combinedto form a storage bag that may be used according to the presentinvention.

FIG. 4 illustrates a fragmentary section taken along section line a-a inFIG. 1 or FIG. 7 of a face-to-face seal according to any embodiment ofthis invention.

FIGS. 5 and 6 illustrate fragmentary sections taken along section linea-a in FIG. 1 or FIG. 7 of a lapped seal according to any embodiment ofthis invention.

FIG. 7 illustrates a plan view of a flexible bag 18 having analternative seal plan, which can be substituted in FIG. 1 in anyembodiment, with the flexible bag 18 partially cut away to illustrateits interior.

The following reference characters are used in this description and theaccompanying drawings.

 10 Container  12 External package  14 Package body  16 Package lid  18Flexible bag 20a Film sheet 20b Film sheet  22 Seal  24 Spout  26Opening (in 12)  28 End seal  30 Barrier coating  32 Surface portion  34Lapped seal  36 Face-to-face seal  38 Side seal  40 Perimeter seal  42Valve (of 24)  44 Solvent  46 Lumen  48 Fused portion 100 PECVDapparatus (FIG. 2) 102 Polymer film (FIG. 2) 104 Unwind reel 106 Quickroller 108 Guide roller 110 Rewind reel 112 Chamber 114 Treatment area116 Diffusion pump 118 Gas inlet 120 Unbalanced magnetron 122 Plasmaenergy source 124 Cathode 202 Polymer film (FIG. 3)

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully with reference tothe accompanying drawings, in which several embodiments are shown. Thisinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth here. Rather,these embodiments are examples of the invention, which has the fullscope indicated by the language of the claims. Like numbers refer tolike elements throughout.

The present invention is directed to containers and methods of makingthe same, preferably for storage of high purity solvents. Such solventsmay include, for example: acetonitrile, dichloromethane (methylenechloride), ethyl ether, hexane, methanol, toluene, acetone, benzene,chloroform, diethyl ether, dimethylformamide, dimethyl sulfoxide,ethanol, heptane, isopropanol, pyridine, tetrahydrofuran and water. In apreferred embodiment, the high purity solvent stored in a containeraccording to the present invention is hexane.

Referring to FIG. 1, there is shown an embodiment of a container 10according to the present invention. The container 10 is optionallyconstructed using standard methods for making wine boxes. Wine boxesgenerally include wine contained in a plastic bag. The plastic bag isretained in a box (usually cardboard), which provides a protective shelland rigid structure for retaining the bag. Examples of wine boxes andprocesses for making the same are disclosed in U.S. Pat. Nos. 3,474,933and 4,274,554 and U.S. Pat. App. Pub. No. 2012/0255971, all of which areincorporated by reference herein in their entireties.

The embodiment of the container 10 according to the present inventionincludes an external package 12, optionally comprising a package body 14and package lid 16, although a unitary package is also within the scopeof the present invention. The external package 12 is preferablyconstructed from an inexpensive rigid or semi-rigid material, such ascardboard, plastic or a soft metal (e.g., aluminum).

The container 10 further includes a sealed flexible bag 18 forcontaining a liquid, such as a high purity solvent (preferably hexane).The bag, which is retained within the external package 12, is preferablyconstructed from polyethylene or another thin, flexible polymer withsimilar physical properties to polyethylene. The flexible bag 18 is madeof at least one film sheet 20 having major surface portions 32.

The film sheets 20 may alternatively be packaging laminates of anynumber of different layers, which can include water vapor sealinglayers, support layers, heat sealable layers, decorative layers, printlayers, tie layers, and the like. Such laminates are well known in thepackaging industry, and need not be described in detail here.

A barrier coating 30 from 2 to 1000 nanometers (nm) thick, optionallyfrom 10 to 200 nm thick, optionally from 20 to 200 nm thick, optionallyfrom 20 to 30 nm thick, is optionally provided on at least one majorsurface portion 32. For the purposes of the present disclosure thethickness of the SiOx coating or layer or other barrier coating or layeris determined by transmission electron microscopy (TEM). Optionally inany embodiment, the bather coating 30 comprises or consists essentiallyof SiOx, in which x is from about 1.5 to about 2.9, or 1.5 to about 2.6,or about 2, or about 2.3. For the purposes of the present disclosure thevalue of x, and thus the ratio of silicon to oxygen, is determined byx-ray photoelectron spectroscopy, commonly known as XPS. Optionally,other types of barrier layers can instead be used.

The barrier coating 30 optionally faces the lumen 46, as is desirablewhen the barrier layer 30 functions to protect the film sheet 20 fromthe contents of the lumen 46. In an embodiment, the film sheet 20 hasfirst and second major surfaces 32 on opposite sides of the sheet 20 andthe barrier coating 30 is on the first major surface 32 only, preferablydefining the interior surface, illustrated in FIGS. 4 and 5. Optionally,the barrier coating 30 is coextensive with the first major surface 32,although it could optionally extend into the seal 22 but not all the wayto the extreme side edge at the outside of the seal.

Another advantage of providing a barrier coating 30 on the insidesurface of the flexible bag 18, is that this protects the barriercoating 30 somewhat from abrasion and other damage during handling andtransportation. Optionally in any embodiment, each of the facing majorsurface portions 32 is at least partially coated with the barriercoating 30. Optionally, each of the facing major surfaces 32 is entirelycoated with the barrier coating 30, completely enveloping the lumen 46without interruption (except in the vicinity of the spout 24, which canbe made in such a fashion as to prevent leakage or permeation by thecontents of the flexible bag 18). This embodiment is illustrated in FIG.6, and is also an option in the embodiment of FIG. 4.

At least one seal 22 is provided between facing major surface portions32. The reference character 22 in this disclosure or the drawingsindicates a seal generically. Seals 22 having various forms are morespecifically defined as a face-to-face seal 36 as illustrated in FIG. 4,a lapped seal 34, illustrated in FIGS. 5 and 6, an end seal 28,illustrated in FIG. 7, and a side seal 38, also illustrated in FIG. 7.While end seals 28, side seals 38, and perimeter seals 40 commonly areface-to-face seals, lapped seals 34 can alternatively be used in anyembodiment. Other seal types and patterns can also be used, withoutlimitation. At least one film sheet 20 and at least one seal 22 define aflexible bag 18 comprising a lumen 46.

The barrier coating 30 optionally extends into the seal 22. The barriercoating 30 extends into the seal 22 as defined in this specification if,in the seal as assembled, the barrier coating 30 is located between thefused portions 48 of the respective film sheets 20 that are joined.Thus, FIGS. 4, 5, and 6 all illustrate a barrier coating 30 extendinginto the seal 22. The embodiment of FIG. 4, in which barrier coatings 30on both sides of the seal 22 extend into the seal is preferred, althoughthe embodiments of FIGS. 5 and 6, in which a barrier coating on only oneside of the seal extends into the seal, are also contemplated,particularly when the primary concern is providing a barrier to ingressof oxygen, rather than an internal barrier to egress of the solvent orother fluid contents 44.

It is contemplated that the barrier coating 30, which is extremely thinand has very little volume, will not prevent the use of heat sealing orultrasonic sealing methods to fuse the adjacent film sheets 20,providing the facing surfaces of the film sheets 20 are directlyheat-sealable to each other. It is further contemplated that in theprocess of heat or ultrasonic sealing, the portion of the barriercoating 30 extending into the seal 22 will be disrupted, allowing directcontact between the adjacent film sheets 20. After sealing, the barriercoating 30 is still regarded as extending into the seal if it waspresent before the seal was effected, whether or not it can be detectedwithin the finished seal. Alternatively, however, the seal can beeffected by placing an adhesive between the surfaces sealed together, asis well known.

The bag 18 is optionally made from a single two dimensional polymer filmsheet that is formed into a three dimensional bag. This embodiment isillustrated in FIG. 7, showing a single sheet 20 in which each side hasbeen folded inward, with the free ends of the respective sidesregistered and sealed together to form the side seal 38. The respectiveends have been sealed with end seals 28. Thus, the flexible bag 18 isformed from a single film sheet 20 joined by a side seal 38 and firstand second end seals 28.

Alternatively, the bag 18 can be made from two or more separate(originally two dimensional) film sheets 20 a, 20 b, which are joinedtogether and sealed along a seal (also known as a spine) 22 according toknown methods, to form a three dimensional bag 18, as illustrated inFIG. 1. In this embodiment, the two sheets 20 a and 20 b are joined by aperimeter seal 40.

Optionally, the bag 18 includes an openable spout 24, which is adaptedto seat within an opening 26 in the external package 12. A user wishingto release liquid contents (e.g. a high purity solvent) from the bag 18when the bag 18 holds such contents may open the spout 24.

The bag 18, as described above, is made from one or more two dimensionalpolymer film sheets. According to an aspect of the present invention,before the one or more polymer film sheets are used to construct thebag, they are coated, e.g. on one side or both sides, with an SiO_(x)coating or layer, preferably using plasma enhanced chemical vapordeposition (PECVD). It is contemplated that a two dimensional polymerfilm sheet, e.g., polyethylene, is an optimal surface on which to applyan SiO_(x) coating or layer because a flat film is less prone to havingsurface imperfections that can affect the integrity of a SiO_(x) coatingthan, e.g., the internal surface of a three dimensional container. Withfewer such surface imperfections, there is a lower likelihood orincidence of unevenness of coating, missed spots, surface imperfectionsand cracking, than a conventional three dimensional SiO_(x) coatedplastic container. As such, it is contemplated that high purity solventsheld in a container according to the present invention would have lessof an opportunity to contact and attack the polymer substrate of the bag18 than would a conventional three dimensional SiO_(x) coated plasticcontainer.

Optionally, the SiO_(x) coating may be part of a coating set. Forexample, a tie coating or layer, a barrier coating or layer, and a pHprotective coating or layer, collectively referred to herein as a“trilayer coating,” may be applied to the flexible sheet of the bag.With a trilayer coating, the barrier coating or layer of SiO_(x)optionally is protected against contents having a pH otherwise highenough to remove it by being sandwiched between the pH protectivecoating or layer and the tie coating or layer, each being optionally anorganic layer of SiO_(x)C_(y) as defined in this specification.

Optionally, the tie coating or layer comprises SiOxCy or SiNxCy,preferably can be composed of, comprise, or consist essentially ofSiOxCy, wherein x is from about 0.5 to about 2.4 and y is from about 0.6to about 3. The atomic ratios of Si, O, and C in the tie coating orlayer 34 optionally can be: Si 100:O 50-150:C 90-200 (i.e. x=0.5 to 1.5,y=0.9 to 2); Si 100:O 70-130:C 90-200 (i.e. x=0.7 to 1.3, y=0.9 to 2);Si 100:O 80-120:C 90-150 (i.e. x=0.8 to 1.2, y=0.9 to 1.5); Si 100:O90-120:C 90-140 (i.e. x=0.9 to 1.2, y=0.9 to 1.4); or Si 100:O 92-107:C116-133 (i.e. x=0.92 to 1.07, y=1.16 to 1.33). The atomic ratio can bedetermined by XPS. Taking into account the H atoms, which are notmeasured by XPS, the tie coating or layer 34 may thus in one aspect havethe formula SiwOxCyHz (or its equivalent SiOxCy), for example where w is1, x is from about 0.5 to about 2.4, y is from about 0.6 to about 3, andz is from about 2 to about 9. Typically, tie coating or layer 34 wouldhence contain 36% to 41% carbon normalized to 100% carbon plus oxygenplus silicon.

Optionally, the tie coating or layer can be similar or identical incomposition with the pH protective coating or layer described elsewherein this specification, although this is not a requirement.

Optionally, the tie coating or layer is on average between 5 and 200 nm(nanometers), optionally between 5 and 100 nm, optionally between 5 and20 nm thick. These thicknesses are not critical. Commonly but notnecessarily, the tie coating or layer 34 will be relatively thin, sinceits function is to change the surface properties of the substrate.Optionally, the tie coating or layer is applied by PECVD, for example ofa precursor feed comprising octamethylcyclotetrasiloxane (OMCTS),tetramethyldisiloxane (TMDSO), or hexamethyldisiloxane (HMDSO).

Certain bather coatings or layers such as SiOx as defined here have beenfound to have the characteristic of being subject to being measurablydiminished in barrier improvement factor in less than six months as aresult of attack by certain relatively high pH contents of the coatedvessel as described elsewhere in this specification, particularly wherethe barrier coating or layer directly contacts the contents. Barrierlayers or coatings of SiOx are eroded or dissolved by some fluids, forexample aqueous compositions having a pH above about 5. Since coatingsapplied by chemical vapor deposition can be very thin—tens to hundredsof nanometers thick—even a relatively slow rate of erosion can remove orreduce the effectiveness of the barrier layer in less time than thedesired shelf life of a product package. This is particularly a problemfor aqueous fluids having a pH of from 4 to 9. The higher the pH of thecontents of a coated container or bag, the more quickly it erodes ordissolves the SiOx coating.

The pH protective coating or layer optionally provides protection of theunderlying barrier coating or layer against contents of the bag 18having a pH from 4 to 9, including where a surfactant is present.

Applicant has found that certain pH protective coatings or layers ofSiOxCy or SiNxCy formed from polysiloxane precursors, which pHprotective coatings or layers have a substantial organic component, donot erode quickly when exposed to fluids, and in fact erode or dissolvemore slowly when the fluids have pHs within the range of 4 to 8 or 5 to9. For example, at pH 8, the dissolution rate of a pH protective coatingor layer made from the precursor octamethylcyclotetrasiloxane, or OMCTS,is quite slow. These pH protective coatings or layers of SiOxCy orSiNxCy can therefore be used to cover a barrier layer of SiOx, retainingthe benefits of the barrier layer by protecting it from the fluid in thebag. The protective layer is applied over at least a portion of the SiOxlayer to protect the SiOx layer from contents stored in a vessel, wherethe contents otherwise would be in contact with the SiOx layer. The pHprotective coating or layer optionally is effective to keep the barriercoating or layer at least substantially undissolved as a result ofattack by the fluid for a period of at least six months.

The pH protective coating or layer 38 can be composed of, comprise, orconsist essentially of SiwOxCyHz (or its equivalent SiOxCy) or SiwNxCyHzor its equivalent SiNxCy), each as defined previously, preferablySiOxCy, wherein x is from about 0.5 to about 2.4 and y is from about 0.6to about 3. The atomic ratios of Si, O, and C in the pH protectivecoating or layer 286 optionally can be: Si 100:O 50-150:C 90-200 (i.e.x=0.5 to 1.5, y=0.9 to 2); Si 100:O 70-130:C 90-200 (i.e. x=0.7 to 1.3,y=0.9 to 2); Si 100:O 80-120:C 90-150 (i.e. x=0.8 to 1.2, y=0.9 to 1.5);Si 100:O 90-120:C 90-140 (i.e. x=0.9 to 1.2, y=0.9 to 1.4); or Si 100:O92-107:C 116-133 (i.e. x=0.92 to 1.07, y=1.16 to 1.33); or Si 100:O80-130:C 90-150.

The thickness of the pH protective coating or layer as appliedoptionally is between 10 and 1000 nm; alternatively from 10 nm to 900nm; alternatively from 10 nm to 800 nm; alternatively from 10 nm to 700nm; alternatively from 10 nm to 600 nm; alternatively from 10 nm to 500nm; alternatively from 10 nm to 400 nm; alternatively from 10 nm to 300nm; alternatively from 10 nm to 200 nm; alternatively from 10 nm to 100nm; alternatively from 10 nm to 50 nm; alternatively from 20 nm to 1000nm; alternatively from 50 nm to 1000 nm; alternatively from 50 nm to 800nm; optionally from 50 to 500 nm; optionally from 100 to 200 nm;alternatively from 100 nm to 700 nm; alternatively from 100 nm to 200nm; alternatively from 300 to 600 nm. The thickness does not need to beuniform throughout the vessel, and will typically vary from thepreferred values in portions of a vessel.

Optionally, the pH protective coating or layer is at least coextensivewith the barrier coating or layer. The pH protective coating or layeralternatively can be less extensive than the barrier coating, as whenthe fluid does not contact or seldom is in contact with certain parts ofthe barrier coating absent the pH protective coating or layer. The pHprotective coating or layer alternatively can be more extensive than thebarrier coating, as it can cover areas that are not provided with abarrier coating.

The pH protective coating or layer 38 optionally can be applied byplasma enhanced chemical vapor deposition (PECVD) of a precursor feedcomprising an acyclic siloxane, a monocyclic siloxane, a polycyclicsiloxane, a polysilsesquioxane, a monocyclic silazane, a polycyclicsilazane, a polysilsesquiazane, a silatrane, a silquasilatrane, asilproatrane, an azasilatrane, an azasilquasiatrane, an azasilproatrane,or a combination of any two or more of these precursors. Someparticular, non-limiting precursors contemplated for such use includeoctamethylcyclotetrasiloxane (OMCTS).

Referring to FIGS. 2 and 3, there are shown alternative embodiments ofapparatus 100, 200, which may be used to apply PECVD SiO_(x) coatings toflat flexible polymer films 102, 202, e.g., polyethylene. It ispreferred that the coatings are applied in a bulk manufacturing processto rolls of the polymer films. The roll of coated film may then beseparated into separate sheets according to known methods forconstructing bags.

The respective PECVD coating apparatus of FIGS. 2 and 3 includes anunwind reel 104, guide rollers 106 and 108 and a rewind reel 110 toconvey the film 102 or 202 within the chamber 112 through a treatmentarea 114. The chamber 112 is evacuated to a suitable pressure by thevacuum pumps 116. A gas inlet 118 is provided to introduce chemicalvapor deposition precursors and reactants for forming the SiO_(x) orother barrier coating. Plasma is generated in the treatment area 114 ofFIG. 2 by an unbalanced magnetron 120 powered by an alternating currentpower source 122. Plasma is generated in the treatment area 114 of FIG.3 by a cathode 124.

Processes for applying PECVD coatings to these rolls of film aredescribed, for example in the following articles, which are incorporatedherein by reference in their entireties: (1) L. Wood and H. Chatham, “AComparison of SiO₂ Barrier Coated Polypropylene to Other Coated FlexibleSubstrates,” 35^(th) Annual Technical Conference Proceedings, Society ofVacuum Coaters (1992); (2) J. Fahlteich, N. Schiller, M. Fahland, S.Straach, S. Günther, and C. Brantz, “Vacuum Roll-to-Roll Technologiesfor Transparent Barrier Films,” 54^(th) Annual Technical ConferenceProceedings, Society of Vacuum Coaters, Chicago, Ill. Apr. 16-21, 2011;and (3) J. T. Felts, 36^(th) Annual Technical Conference Proceedings,Society of Vacuum Coaters (2011).

While the invention has been described in detail and with reference tospecific examples thereof, it will be apparent to one skilled in the artthat various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

1. A container comprising an external package and a sealed flexible bagadapted to hold liquid contents retained within the external package,the bag comprising a polymer film, which prior to being formed into abag, was a two dimensional film to which was applied a PECVD SiOxcoating.
 2. The container of claim 1, wherein the external packagecomprises one or more rigid or semi-rigid materials selected from thegroup consisting of plastic, cardboard and a soft metal.
 3. Thecontainer of claim 1, wherein the polymer film is polyethylene.
 4. Thecontainer of claim 1, wherein the bag holds a high purity solvent. 5.The container of claim 4, wherein the high purity solvent is hexane. 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. (canceled) 11.(canceled)
 12. (canceled)
 13. (canceled)
 14. (canceled)
 15. (canceled)16. (canceled)
 17. (canceled)
 18. (canceled)
 19. The flexible bag ofclaim 6, in which the barrier coating consists essentially of SiOx, inwhich x is from about 1.5 to about 2.9.
 20. The flexible bag of claim 6,in which the barrier coating is from 10 to 200 nm thick, optionally from20 to 200 nm thick, optionally from 20 to 30 nm thick.
 21. The flexiblebag of claim 6, in which the film sheet has first and second majorsurfaces on opposite sides of the sheet and the barrier coating is onthe first major surface only.
 22. The flexible bag of claim 6, in whichthe barrier coating is coextensive with the first major surface. 23.(canceled)